The invention relates to a disposable double pointed injection needle having an injection part with a skin piercing end and a cartridge part for inserting into a cartridge containing a liquid medicine to be injected subcutaneously. The cannula of the injection needle is fastened in a needle hub for mounting on a syringe, which syringe supports the cartridge into which the cartridge part of the injection needle penetrates.
The invention further relates to an insulin injection system comprising a pen shaped syringe supporting a cartridge with insulin, a dose setting and injection mechanism and a disposable double pointed injection needle.
Injections where a liquid is expelled into the human body are usually performed either as intramuscular injections i.e. injections into the muscle tissue, or as subcutaneously injections i.e. injections into the subcutaneous tissue lying between the cutis and the muscle tissue.
When performing intramuscular injections of a vaccine it is according to British Medical Journal, volume 321, p. 931, important to use long injections needles in order to avoid local reactions such as redness and swelling. According to the article, use of injection needles having a length of 25 mm reduced the rate of local reaction significantly compared to an injection needle having a length of 16 mm.
Long injection needles must have a relatively large diameter in order not to break during injection. The injection needles referred to in the above mentioned article has a diameter of 23 G for the 25 mm long injection needle and 25 G for the 16 mm long injection needle.
The outside diameters of injection needles are indicated by a xe2x80x9cGxe2x80x9d and a gauge number increasing with thinner needles. Thus the outside diameter of a G 23 is 0.60 mm and of a G 25 0.50 mm.
It has for some years been known to provide long injection needles with safety protective devices in order to prevent accidental needle stick injuries. Such safety protective devices are e.g. known from EP 409.180 and U.S. Pat. No. 4.813.940. These known safety protective devices comprises a number of telescopic sleeves, which telescopic sleeves slides into each other in order to expose an injection needle covered by the telescopic sleeves when not in use. The injection needles used has opposite the skin piercing end a needle connector for connecting the injection needle with an ordinary hypodermic syringe. By the expression xe2x80x9cordinary hypodermic syringexe2x80x9d is meant a syringe of the type where the medicine to be injected is drawn from a vial into the syringe prior to each injection. In practical use the medicine has to flow through the injection needle twice for every injection when using such an ordinary hypodermic syringe, but due to the large diameter and the large bore of a long injection needle clogging is not a problem.
U.S. Pat. No. 5.429.612 discloses yet another long injection needle having a safety protective sleeve which can be moved into a position where the safety protective sleeve covers the injection part of the needle cannula. As can be seen in FIG. 1 of U.S. Pat. No. 5.429.612 the injection part of the needle cannula has a length, which makes it necessary to support the needle cannula by at least one disk 21. The syringe is loaded with a flask containing the medicament to be injected. Since the syringe has no dose setting and injection mechanism like the ones known from insulin injection pens, the entire content of the flask is emptied into the patient in one injection, which is the usual procedure when injecting anaesthesia in dentistry. When using the embodiments shown in FIGS. 2 and 3, the user must manually rotate the shield after use in order to bring the tongue 26 from the first track 23 and into the second track 24. Doing so the user is exposed to a great danger, since the rotation must be done after the contaminated needle cannula has been retracted from the body of the patient.
When providing long injection needle with safety protective sleeves there are hardly any limitation to the length of the injection needle as long as the relationship between the length and the diameter is sufficient to prevent unwanted needle breakage. The muscular tissue is in a human body normally located approximately 10 to 14 mm below the surface of the skin. The part of a long injection needle entering the human body therefore has to be at least 14 mm in order to reach into the muscular tissue of the human body. As can be seen from the prior art injection needles, the length of the needle cannula from its fastenings point in the needle connector to its skin piercing end is substantially longer than the part of the needle cannula, which enters the human body during injection. This presents however no problem since these needle has a large diameter sufficient to withstand breakage.
Some medicines however has to be injected subcutaneously i.e. in the subcutis lying between the cutis and a muscle membrane which cover the underlying muscles. If for instead insulin for treating diabetes is injected into the muscle tissue it will be absorbed in the body to quickly and an unwanted drop in the blood sugar may be the result. In order to prevent intramuscular injection of insulin it is quite common for people suffering from diabetes to inject into a lifted skin fold. It is however becoming more and more preferred by diabetic persons to inject directly at an angle of 90xc2x0 without the skin fold, using an extra short needle. The extra short needle must have an overall length of the injection part of the needle cannula short enough to avoid intramuscular injections. Such extra short needles are e.g. known from WO 97.23253, which discloses an injection needle having an overall length of the injection part laying in the interval 4 to 6 mm.
Very short injection needle are not subject to breakage in the same degree as long injection needles, and can therefore be made with a much smaller diameter. WO 93.00948 reveals a short injection needle, having an injection part in the interval 8 to 12 mm, for injecting insulin. The diameter of the needle cannula is thinner than G 29. Such short and thin needles cannot be used in connection with an ordinary hypodermic syringe where the medicine is drawn up from a vial prior to each injection since this requires the medicine to flow through the needle twice for every injection, which can result in clogging of the bore of the injection needle, especially if the medicine is a suspension. However when the short and thin needle are used in connection with a syringe supporting a cartridge containing the medicine to be injected, the medicine only has to flow through the injection needle once which in itself halves the risk of clogging, and thereby allows very thin injection needles to be used. At the same time, when an injection needle has only a small diameter both outside and inside, the pressure needed to force a liquid through the bore of the injection needle is high when the injection needle is long, but substantially smaller if the injection needle is short.
These known short and thin injection needles are however not provided with any safety protective devices, while the safety protective sleeves known from the prior art would permanently cover a large part of the injection part of the injection needle thereby preventing a short injection needle from penetrating through the cutis layer, which layer usually is between 2 to 3 mm thick, and into the subcutis layer of a human body.
Injection needles with relatively thin diameter and with a length of the injection part of the needle cannula between 4 to 12 mm are often used for self-injection of insulin i.e. where the patient injects him or herself. However for self-injection in private settings, safety protective devices providing safety against accidental needle stick injuries are not considered to be important, since no other person beside the patient performing the self-injection has contact with the injection needle. Safety protective devices providing safety against accidental needle stick injuries would however be preferred in domestic residences if other people, and especially children, are present in the domestic residence.
It is however very important in hospital settings where many people interacts to use injection needles, which are provided with some kind of safety protective device preventing accidental needle stick injuries. All the prior art injection needles provided with safety protective devices are long injection needles for intramuscular injections. These long injection needles are often of the type used on traditional hypodermic syringes where the medicine has to flow through the bore of the needle twice for every injection thereby limiting the minimum diameter of the bore and the outside diameter of the injection needle. Hospitalised people suffering from diabetes are usually injected with these long injection needles having a relatively large outside diameter. This is also the case with senior citizens in retirement homes, with children in schools and in day-care facilities, in fact every place an insulin injection is performed by a professional health care worker long injection needles are used, since they are the only ones providing sufficient safety for the health care worker. The health care worker giving the injection using a long needle has to be very careful only to penetrate into the subcutis layer in order for the insulin to be correctly absorbed in the human body, and at the same time the large diameter of a long injection needle gives the patient a high pain perception. No matter how careful health care workers are when injecting insulin, the insulin will sometimes unintended be injected into the muscle tissue, with the subsequent changes in insulin absorption and diabetes control. Patients which are newly diagnosed with diabetes and not familiar with self-injection often finds a long injection needle with a large diameter very intimidating, which is also the case with children. At the same time needles with large diameters tends to fracture the skin more than thin needles.
It is an object of the present invention is to provide a short and thin disposable double pointed injection needle for subcutaneously injection, which overcomes the deficiencies of the prior art. It is further an object to provide a short and thin disposable double pointed injection needle which is equipped with a safety protective device preventing accidental needle stick injuries, and which injection needle could be used on a modern type syringe supporting a cartridge containing a liquid medicine.
This is obtained by a disposable double pointed injection needle according to claim 1.
The short and thin injection needle is provided with a movable needle protector which allows normal use of the injection needle during injection, and which movable needle protector once the injection is done can be shifted manually or automatically into a position where the movable needle protector covers the skin piercing end of the needle cannula in an irreversible manner. When the skin-piercing end of the cannula is covered, the injection needle can be removed from the syringe and disposed off without endangering the people performing the injection and the people disposing of the used injection needles. The cartridge part of the needle cannula is permanently covered by the hub preventing the cartridge part of the needle cannula from accidental penetrating the skin of the persons handling the injection needle.
Hospitalised people suffering from diabetes or a similar disease is hereby provided with a disposable double pointed injection needle which only penetrates into the subcutis layer of the human body during injection and which at the same time offers sufficient protection against accidental needle sticks. This will relieve the patients from the variations in the depth of penetration occurring when injections are given using long injection needles and provide safety for the health care workers at the same time. Since the disposable double pointed injection needle is both short and thin, the pain perception will be very low.
Since especially children are very sensible to the appearance of the injection needle, a short disposable double pointed injection needle where a major part of the injection part of the needle cannula is hidden inside the boundaries of a safety shield prior to injection will make it psychologically easier for a child to accept the fact that daily injections of a liquid medicament such as insulin or growth hormone is needed.
When as disclosed in claim 2, the movable needle protector is a cylinder-shaped safety shield surrounding at least the major part of the injection part of the needle cannula when the needle cannula is in an unused state, and which cylinder-shaped safety shield can be longitudinal moved relatively to the needle cannula, such that the safety shield is first moved in the proximal direction when the injection part of the cannula is penetrated into the subcutis layer of a human body, thereby exposing the major part of the injection part to the human body, and which safety shield automatically moves in the distal direction until the cannula is fully surrounded by the safety shield when the injection part of said cannula is removed from the subcutis layer of a human body, it is ensured that the entire injection part of the needle cannula is securely covered at all times during the injection.
In a preferred embodiment of the disposable double pointed injection needle according to the invention the safety shield is automatically moved in the distal direction when the injection part of the cannula is removed from the subcutis layer of the human body by a resilient element such as a helical spring, which resilient element is located between the needle hub and the safety shield, and which resilient element is tighten when the injection part of said cannula is penetrated into the subcutis layer of the human body. Such an automatic movement by a spring or another resilient element ensures that the shield is always moved into the position where its covers the injection part of the needle cannula without the need of the user to manually push the shield into this position. Any type of resilient element can be utilized, although it is preferred to use a helical spring. Such a helical spring can be either metallic or made from a polymeric material.
When as disclosed in claim 4, the safety shield is guided on the outside surface of the needle hub, it is ensured that the safety shield can be pushed all the way back such that a major part of the injection part of the needle cannula of the injection needle is exposed to the human body during injection thereby limiting the overall length of the needle cannula of the injection needle.
When, as disclosed in claim 5, the safety shield is provided with a number of inwardly pointed projections guided in guiding tracks provided on the external surface of the needle hub, it is ensured that the shield moves relatively to the needle cannula and the needle hub in a predetermined pattern.
In yet a preferred embodiment of the disposable double pointed injection needle according to the invention at least two guiding tracks are located opposite each other on the needle hub each comprises a first part being substantially parallel to the needle cannula and a second part being connected to the first part at an acute angle. Two, three or more guiding tracks provide stability to the shield, and an acute angle between the two parts of each track provides a smooth movement of the shield.
When, as disclosed in claim 7, one of the parts of the guiding tracks is open at the distal end of the needle hub allowing the projections to enter each guiding track, and that the open part of each guiding track at the distal end is provided with an elevation, it is ensured that the projections are easily inserted in the tracks, and that once located in the guiding tracks is prevented from sliding out of grip with the guiding track. The part of the guiding tracks being open at the distal end can either be the first part or the second part.
In another embodiment of the disposable double pointed injection needle according to the invention, each projection can be shifted between three different locations in the guiding track:
a first location where the safety shield surrounds at least the major part of the injection part of said cannula, and in which location said needle cannula is in an unused state
a second location where the major part of the injection part is exposed to the human body, and in which location the needle cannula is penetrated into the human body, and
a third location where the safety shield fully surrounds the injection part of the cannula, and in which location the cannula is fully removed from the human body.
By having the projections and the shield move relatively to the needle hub in the pattern described in claim 8, it is ensured that the major part of the needle cannula extending in the distal direction from the needle hub is inserted into the human body during injection.
When, as disclosed in claim 9, at least one of the guiding track has at least one elevation with a steep front preventing the projection from moving backwards in the guiding track when the projection has entered the second or/and the third position, it is ensured that the safety shield can not be moved in the backward direction once an injection has commenced
When, as disclosed in claim 10, one of the elevations is formed as a hole or a well located at the end of one of the guiding tracks near to the distal top end of the needle hub, and the projection drops into the hole or well when the projection is in the third location, such that the safety shield is irreversible locked to the needle hub when said cannula is fully removed from the human body, it is ensured that the safety shield is irreversible locked to the needle hub when the needle cannula is fully removed from the human body thereby preventing reuse of said injection needle.
When, as disclosed in claim 11, the disposable double pointed injection needle further comprises a container surrounding the needle hub, the needle cannula, the resilient element and the safety shield, and which container has inwardly pointing ribs engaging similar outwards pointing ribs on the needle hub, it is ensured that the rotational force emerging when the container is rotated is transferred to the needle hub.
It is also an object of the present invention to provide a pen based insulin injection system, which can be used in hospital settings or other public places without exposing the professional people working in these places to accidental needle stick injuries.
This is obtained by an insulin injection system according to claim 12.
By having a complete system comprising both a pen shaped syringe supporting a cartridge and a short and thin safety engineered injection needle with a needle protector, a complete pen based injection system for the treatment of diabetes can now be used in hospitals only using needle-based medical devices designed to provide health care workers with additional protection against accidental needle stick injuries and potential exposure to infectious diseases.
In one embodiment of the disposable double pointed injection needle according to the invention the injection needle is further provided with means providing the user with a visual indication when the injection needle is in a potentially unsafe position. In another embodiment of the disposable double pointed injection needle according to the invention the injection needle is further provided with means providing the user with a visual indication when said disposable double pointed injection needle is in a potentially safe position. As the disposable double pointed injection needle according to the invention has previously been described it is somewhat difficult for the user to visible inspect if the disposable double pointed injection needle has been used. This problem is overcome by providing the disposable double pointed injection needle with means according to claim 13 and/or 14.
When, as disclosed in claim 15, the means providing the user with a visual indications comprises at least one transparent area in the movable needle protector and at least one first area and/or at least one second area located on the outside surface of the needle hub, and as disclosed in claim 16, the first areas located on the outside surface of the needle hub is visible through the transparent areas when the projection is in the first location, and/or that said second areas located on the outside surface of the needle hub is visible through the transparent areas in said movable needle protector when the projection is locked in said third location, it becomes very simple for an user to inspect whether the disposable double pointed injection needle is unused or not.
When, as disclosed in claim 17, the first areas and/or the second areas are provided with different colours or symbols, it is ensured that even users with poor sight can visible inspect whether the disposable double pointed injection needle has been used or not.
In the present context, the term xe2x80x98injectionxe2x80x99 is taken to mean expelling a liquid along a hollow needle or another hollow conduit and into a human body, in which human body a part of the hollow needle or conduit is temporarily inserted.
Although the wording xe2x80x9chuman bodyxe2x80x9d is used through out this application, the disposable double pointed injection needle claimed could as well be used on any mammal body without dispersing from the scope of the claims.
In the present context, the term xe2x80x9ccartridgexe2x80x9d is taken to mean a hollow tube-like container having one end permanently sealed by a membrane, which membrane is penetrated by the cartridge part of the needle cannula when the double pointed injection needle is attached to the cartridge or the syringe. The other end of the cartridge is a displaceable plate or cylinder that fits tightly against the inner walls of the cartridge. A discrete dose is expelled through the double pointed injection needle attached to the cartridge or the syringe if the plate or cylinder is displaced in the direction towards the permanent membrane penetrated by the cartridge part of the double pointed injection needle.
The cartridge containing the medicine is usually supported in the distal end of the housing of the syringe. The cartridge can either be permanently fastened in the housing or it can be exchangeable. If the cartridge is permanently fastened in the housing, the entire syringe is disposed of when the cartridge is empty, but if the cartridge is exchangeable then only the empty cartridge is disposed of and a new, full cartridge is loaded into the housing of the syringe.
It is to be understood that the wording xe2x80x9cpen shaped syringexe2x80x9d, used throughout this application, merely refers to a syringe having an oblong or elongated shape and which fits into one hand, somewhat like a pen for writing. Although such writing pens usually have a tubular cross-section, modern writing pens often have a different cross-section such as triangular, rectangular or square. Pen shaped syringes can in a similar way have a large variety of different cross-sections.
When referring to the disposable double pointed injection needle according to the present application the term xe2x80x9crelatively thin outside diameterxe2x80x9d is taken to mean a needle cannula having an outside diameter thinner than G28. The use of G28 needle cannulas for injecting insulin has for many years been widely accepted as the standard size, and G29 or thinner needle cannulas are therefore often referred to as xe2x80x9cthin injection needlesxe2x80x9d. The needle cannula of the disposable double pointed injection needle can be as thin as 31G or even 32G.
A xe2x80x9cGxe2x80x9d and a gauge number increasing with thinner needles indicate the outside diameter of the needle cannula. The following table indicates the relation between the gauge number and the outside diameter of the needle cannula, for the gauge numbers referred to in the present application.
The part of the needle cannula referred to as the xe2x80x9ccartridge partxe2x80x9d is the part entering the cartridge. which is to be understood as the part extending in the proximal direction from its fastening point in the needle hub, while the part referred to as the xe2x80x9cinjection partxe2x80x9d of the needle cannula is the part entering the human body during injection, which is to be understood as the part extending in the proximal direction from its fastenings point in the needle hub. The injection part extending in the proximal direction from its fastening point in the needle hub is often a little longer than the part actually penetrating into the human body. The length different between the injection part and the part actually penetrating into the human body depends on the height of the hub tower and the wall thickness of the top surface of the safety shield. Usually the part of the needle cannula, which penetrates into the human body has a length between 4 to 12 mm, such that the depth of penetration lies between 4 to 12 mm.
In the present context, the term xe2x80x9cdose setting and injection mechanismxe2x80x9d is taken to mean a mechanism by which a desired dose of a liquid medicine contained in a cartridge can first be set and later injected, leaving the remaining part of the liquid medicine in the cartridge. The mechanism can either be mechanical or electronic, or both. The injection is usually done by having a mechanical element pressing forward the plate or cylinder inside the cartridge in correspondence with the set dose. The force used for driving forward this mechanical element is preferably delivered either physically by the user or by an electrical motor.
In the present context, the term xe2x80x9csubcutaneouslyxe2x80x9d refers to the subcutis layer of the human body, which are the layer located between the cutis and a muscle membrane covering the muscular tissue. By a number of measurements it is found that the average depth of the muscle membrane is 9.5 mm for males and 13.8 for females, measured from the outside of the human skin. Recognizing that the emission of liquid from an injection needle, due to the oblique cut end of the skin piercing end of the needle cannula, takes place in a distance from the skin piercing end in the range 0.4 to 1.2 mm, an injection needle for subcutaneously injections should preferably have an length of the part penetrating into the subcutaneous layer shorter than approximately 10 mm. Although an injection needle having a length of this part, which equals the depth of penetration, up to approximately 14 mm would be acceptable for females. In order to ensure penetration of the cutis of a human being, the minimum length of the part of the needle cannula penetrating the subcutaneous layer must be longer than approximately 4 mm.